The present invention concerns a method related to GPRS (General Packet Radio Service) system providing packet switched connections throughout a communication network, especially a PLMN (Public Land Mobile Network), said connections being related to different QoS (Quality of Service) levels between end users, wherein an LLC (Logic Link Control) protocol is a packet oriented protocol, and wherein an LLC is established when one mobile station activates one PDP context with a QoS for which the MS (Mobile Station) does not already have an LLC establishment.
GPRS, that is currently specified by ETSI as a service for GSM phase 2+, provides packet switched connections throughout the PLMN. The packet switching is performed between the nodes in the network and on the radio interface. It is currently specified for four different quality of service levels in order to offer different types of subscriptions with different demands for the efficiency between the end users.
The most critical part of the transmission is between a mobile station and the SGSN (Serving GPRS Support Node). The change of the mobile stations position and the fact that several users share the same radio resources makes prediction of QoS difficult because of the chosen LLC protocol.
The protocol stack for GPRS (MS-SGSN) is shown in the enclosed FIG. 1.
1. The Problem Area
The nature of the LLC protocol is a packet oriented protocol where the packets must be received in the same order as they are sent. The philosophy has been that one mobile station is assigned one Logic Link where a number of PDP contexts can be activated. The SNDCP layer will multiplex all PDP contexts for one mobile station on the Logic Link. This may result in having one subscriber attached to the GPRS system with e.g. four different PDP contexts, each PDP context with a different QoS. The QoS requirements for GPRS have started discussions whether the BSS (Base Station System) in situations with high traffic may alter the packet flow for a single MS by taking the QoS into account in the packet processing between the MS and the SGSN.
2. Prior Art
The current approach for the GPRS standardization is to have several Logic Links for one mobile station. When one mobile station activates one PDP context with a QoS for which the mobile station does not already have a Logic Link established, a Logic Link is established.
This may result in having one subscriber attached to the GPRS system with e.g. four different PDP contexts, each PDP context with a different QoS and thereby a separate Logic Link.
3. Shortcomings of the Prior Art
The working assumption is complicated. It leads to separate handling of several Logic Links for one mobile station which cause extensive logic in the MS and the SGSN at PDP context activation/deactivation and a change of Logic Link(s) during assignment of new link identities internally within an SGSN and at change of SGSN.
An object of the present invention is to provide an improved method for controlling multiple quality of service levels in a communication network, especially a PLMN (Public Land Mobile Network).
Another object of the present invention is to avoid separate handling of several logic links for one mobile station, so as to avoid extensive logic in any MS and any SGSN at PDP context activation/deactivation.
A further object of the present invention is to have an efficient change of logic link changes.
These objects are achieved by means of a method as stated in the preamble, which according to the present invention is characterized in that the method involves the use of one LL (logic link) with an independent set of link state variables per QoS, so as to allow independent handling of different QoS within said link.
In other words, the proposed solution can be characterized by being one Logic Link (to ease the handling of Logic Link) with an independent set of logic link state variables (LLSV) per QoS (in order to have an independent handling of different QoS within the Logic Link).
It may be possible to acknowledge several QoSs in one supervisory frame using a bit-mapped Logic Link State Variable Indicator.
The invention makes it possible to handle different QoSs at the same Logic Link even though the sequence of frames received at the terminating peer may not be the same as the sequence of the frames sent from the originating peer.
Further features and advantages of the present invention will appear from the following description taken in connection with the appended drawings, as well as from the enclosed patent claims.